1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.content.res;
18
19import android.annotation.NonNull;
20import android.annotation.Nullable;
21import android.content.res.Resources.Theme;
22import android.content.res.Resources.ThemeKey;
23import android.util.LongSparseArray;
24import android.util.ArrayMap;
25
26import java.lang.ref.WeakReference;
27
28/**
29 * Data structure used for caching data against themes.
30 *
31 * @param <T> type of data to cache
32 */
33abstract class ThemedResourceCache<T> {
34    private ArrayMap<ThemeKey, LongSparseArray<WeakReference<T>>> mThemedEntries;
35    private LongSparseArray<WeakReference<T>> mUnthemedEntries;
36    private LongSparseArray<WeakReference<T>> mNullThemedEntries;
37
38    /**
39     * Adds a new theme-dependent entry to the cache.
40     *
41     * @param key a key that uniquely identifies the entry
42     * @param theme the theme against which this entry was inflated, or
43     *              {@code null} if the entry has no theme applied
44     * @param entry the entry to cache
45     */
46    public void put(long key, @Nullable Theme theme, @NonNull T entry) {
47        put(key, theme, entry, true);
48    }
49
50    /**
51     * Adds a new entry to the cache.
52     *
53     * @param key a key that uniquely identifies the entry
54     * @param theme the theme against which this entry was inflated, or
55     *              {@code null} if the entry has no theme applied
56     * @param entry the entry to cache
57     * @param usesTheme {@code true} if the entry is affected theme changes,
58     *                  {@code false} otherwise
59     */
60    public void put(long key, @Nullable Theme theme, @NonNull T entry, boolean usesTheme) {
61        if (entry == null) {
62            return;
63        }
64
65        synchronized (this) {
66            final LongSparseArray<WeakReference<T>> entries;
67            if (!usesTheme) {
68                entries = getUnthemedLocked(true);
69            } else {
70                entries = getThemedLocked(theme, true);
71            }
72            if (entries != null) {
73                entries.put(key, new WeakReference<>(entry));
74            }
75        }
76    }
77
78    /**
79     * Returns an entry from the cache.
80     *
81     * @param key a key that uniquely identifies the entry
82     * @param theme the theme where the entry will be used
83     * @return a cached entry, or {@code null} if not in the cache
84     */
85    @Nullable
86    public T get(long key, @Nullable Theme theme) {
87        // The themed (includes null-themed) and unthemed caches are mutually
88        // exclusive, so we'll give priority to whichever one we think we'll
89        // hit first. Since most of the framework drawables are themed, that's
90        // probably going to be the themed cache.
91        synchronized (this) {
92            final LongSparseArray<WeakReference<T>> themedEntries = getThemedLocked(theme, false);
93            if (themedEntries != null) {
94                final WeakReference<T> themedEntry = themedEntries.get(key);
95                if (themedEntry != null) {
96                    return themedEntry.get();
97                }
98            }
99
100            final LongSparseArray<WeakReference<T>> unthemedEntries = getUnthemedLocked(false);
101            if (unthemedEntries != null) {
102                final WeakReference<T> unthemedEntry = unthemedEntries.get(key);
103                if (unthemedEntry != null) {
104                    return unthemedEntry.get();
105                }
106            }
107        }
108
109        return null;
110    }
111
112    /**
113     * Prunes cache entries that have been invalidated by a configuration
114     * change.
115     *
116     * @param configChanges a bitmask of configuration changes
117     */
118    public void onConfigurationChange(int configChanges) {
119        prune(configChanges);
120    }
121
122    /**
123     * Returns whether a cached entry has been invalidated by a configuration
124     * change.
125     *
126     * @param entry a cached entry
127     * @param configChanges a non-zero bitmask of configuration changes
128     * @return {@code true} if the entry is invalid, {@code false} otherwise
129     */
130    protected abstract boolean shouldInvalidateEntry(@NonNull T entry, int configChanges);
131
132    /**
133     * Returns the cached data for the specified theme, optionally creating a
134     * new entry if one does not already exist.
135     *
136     * @param t the theme for which to return cached data
137     * @param create {@code true} to create an entry if one does not already
138     *               exist, {@code false} otherwise
139     * @return the cached data for the theme, or {@code null} if the cache is
140     *         empty and {@code create} was {@code false}
141     */
142    @Nullable
143    private LongSparseArray<WeakReference<T>> getThemedLocked(@Nullable Theme t, boolean create) {
144        if (t == null) {
145            if (mNullThemedEntries == null && create) {
146                mNullThemedEntries = new LongSparseArray<>(1);
147            }
148            return mNullThemedEntries;
149        }
150
151        if (mThemedEntries == null) {
152            if (create) {
153                mThemedEntries = new ArrayMap<>(1);
154            } else {
155                return null;
156            }
157        }
158
159        final ThemeKey key = t.getKey();
160        LongSparseArray<WeakReference<T>> cache = mThemedEntries.get(key);
161        if (cache == null && create) {
162            cache = new LongSparseArray<>(1);
163
164            final ThemeKey keyClone = key.clone();
165            mThemedEntries.put(keyClone, cache);
166        }
167
168        return cache;
169    }
170
171    /**
172     * Returns the theme-agnostic cached data.
173     *
174     * @param create {@code true} to create an entry if one does not already
175     *               exist, {@code false} otherwise
176     * @return the theme-agnostic cached data, or {@code null} if the cache is
177     *         empty and {@code create} was {@code false}
178     */
179    @Nullable
180    private LongSparseArray<WeakReference<T>> getUnthemedLocked(boolean create) {
181        if (mUnthemedEntries == null && create) {
182            mUnthemedEntries = new LongSparseArray<>(1);
183        }
184        return mUnthemedEntries;
185    }
186
187    /**
188     * Prunes cache entries affected by configuration changes or where weak
189     * references have expired.
190     *
191     * @param configChanges a bitmask of configuration changes, or {@code 0} to
192     *                      simply prune missing weak references
193     * @return {@code true} if the cache is completely empty after pruning
194     */
195    private boolean prune(int configChanges) {
196        synchronized (this) {
197            if (mThemedEntries != null) {
198                for (int i = mThemedEntries.size() - 1; i >= 0; i--) {
199                    if (pruneEntriesLocked(mThemedEntries.valueAt(i), configChanges)) {
200                        mThemedEntries.removeAt(i);
201                    }
202                }
203            }
204
205            pruneEntriesLocked(mNullThemedEntries, configChanges);
206            pruneEntriesLocked(mUnthemedEntries, configChanges);
207
208            return mThemedEntries == null && mNullThemedEntries == null
209                    && mUnthemedEntries == null;
210        }
211    }
212
213    private boolean pruneEntriesLocked(@Nullable LongSparseArray<WeakReference<T>> entries,
214            int configChanges) {
215        if (entries == null) {
216            return true;
217        }
218
219        for (int i = entries.size() - 1; i >= 0; i--) {
220            final WeakReference<T> ref = entries.valueAt(i);
221            if (ref == null || pruneEntryLocked(ref.get(), configChanges)) {
222                entries.removeAt(i);
223            }
224        }
225
226        return entries.size() == 0;
227    }
228
229    private boolean pruneEntryLocked(@Nullable T entry, int configChanges) {
230        return entry == null || (configChanges != 0
231                && shouldInvalidateEntry(entry, configChanges));
232    }
233}
234